Table 161 431 



GEODETIC AND ASTRONOMICAL CONSTANTS 



Dimensions of the earth: 



International Clarke 



ellipsoid spheroid 



of reference x of 1866 2 



Semimajor axis = a 6378388 m. 6378206.4 m. 



Semiminor axis = b 6356911.946 m. 6356583.8 m. 



Mean radius = 2a + b 6371229.315 m. 



Radius of sphere of same area 6371227.709 m. 



Radius of sphere of same volume 6371221.266 m. 



Length of meridian quadrant 10002288.299 m. 



Length of equatorial quadrant 10019148.4 m. 



Area of ellipsoid 510100934 km. a 



Volume of ellipsoid 1083319.78 X 10 e km. 8 



Flattening =/ 1/297 



Note. — The Clarke spheroid of 1866 is the reference spheroid for triangulation in the 

 United States, Canada, and Mexico. The International Ellipsoid of Reference is used in 

 South America and in parts of western Europe. It was adopted in 1924 by the Inter- 

 national Union of Geodesy and Geophysics and its use is recommended by that body 

 wherever practicable. (See Encyclopedia Britannica, 1947 edition, article on Geodesy, for 

 data concerning other spheroids.) 



Mass of the earth 3 5.975 X 10* kg. 



Mean distance earth to sun (astronomical unit) 8 1.4968 X 10 s km. 



Mean linear velocity of the earth in its orbit 29.77 km. sec." 1 



Mean linear velocity of the surface of the earth at the equator . 465.1 m. sec." 1 



Obliquity of the ecliptic 23°27' 



(Also see Table 1, section D, Time.) 



1 U. S. Coast and Geodetic Survey, Spec. Publ. No. 200, 1935. 



•Ibid., Spec. Publ. No. 5, 1946. 



* Russell, H. N., Dugan, R. S., and Stewart, J. Q., Astronomy, Ginn and Co., 1945. 



SMITHSONIAN METEOROLOGICAL TABLES 



